1. Field of the Invention
The invention relates to a steering wheel with an airbag module.
2. Description of the Related Art
In motor vehicle steering wheels the rigid coupling to the steering column gives rise to the problem of vibrations occurring in the steering wheel, at least in certain speed ranges. These vibrations are caused by the natural frequency of the airbag-steering wheel as a function of a certain engine speed. In addition to shifting the natural frequency of the airbag-steering wheel to a frequency range lying outside the range of the oscillations actually occurring on the steering wheel by fitting an additional mass to the steering wheel, DE 37 10 173 A1, for example, discloses an arrangement wherein, in order to reduce the vibrations, a airbag unit is mounted via a vibration-damping housing to the steering wheel in such a way that it is relatively moveable transversely to the longitudinal axis of the steering column in relation to the steering wheel.
In addition, it is proposed that the housing also be moveable in the direction of the longitudinal axis of the steering column. This mobility is achieved in that retaining clips are arranged at the sides of the housing. These have bearing bushes possessing sound-damping characteristics which are disposed in corresponding holes. The bearing bushes guide lock screws for fixing the retaining clips to the spokes of the steering wheel. There is a clearance between the shank of each lock screw and the respective bush, which permits lateral displacement of the retaining clips in relation to the lock screws.
A floating bearing is therefore obtained. In this case the entire airbag module the cap, which screens it off from the compartment, is mounted on a floating bearing.
The disadvantage of this arrangement is that it is relatively expensive.
The object of the invention, therefore, is to obtain a vibration-damped mounting of the airbag in the steering wheel at lower cost.
According to the invention, this is achieved by a steering wheel having airbag module which is supported on the steering wheel by a vibration-damped mounting. In this arrangement the airbag module is connected to the steering wheel by at least one elastic element, which has an isolated area for fixing a retaining element of the airbag module. In particular the elastic element has a bush-shaped first section for fixing to the steering wheel and a bush-shaped second section with isolated area for the fixing of the airbag module, the second section surrounding the first section with clearance and being connected to the first section at one side.
Such an elastic element is easy to manufacture, assemble and connect to the airbag module. The elastic element can thus be connected directly to the steering wheel. In a preferred embodiment, however, the first section is fixed on a rigid bush, which can in turn be connected to the steering wheel by a bolt and nut.
It is advisable for the elastic element to be connected to the airbag module at the isolated end of the second section, since in this case maximum damping is achieved. It is furthermore advisable for the elastic element to be composed of an elastomer.
The elastic element is preferably molded on to a carrier plate for a gas generator.
The internal and external contour of the bush-shaped first and second sections preferably have a circular cross section.
In a further development it is proposed that the first section has an irregular wall thickness, its internal and external contours lying eccentrically to one another, for example. In this way a directional oscillation behavior is achieved.
In a further embodiment it is proposed to design the first bush-shaped section with a taper, the cross section diminishing from the point of connection to the second section onwards, for example.
Furthermore, the second bush-shaped section may also taper, the cross section increasing from the point of connection to the first section onwards, for example.
In a preferred embodiment four elastic retaining elements are provided on a carrier plate for the gas generator.
In a further development it is proposed that the airbag module and a cap for covering it be fixed to the steering wheel separately from one another, the cap being firmly connected to the steering wheel.